Răspuns:
.a= notăm distanța
/ = supra
a/4+13,5=(a+54)/4km prima zi
1/3×a-(a+54)/4+10=
1/3×(3a-54)/4+10
(3a-54)/12=10
(3a+66)/12 km a doua zi
(a +54)/4+(3a+66)/12+5=a×12
3×(a+54)+3a+66+5×12=12×a
3×a +162+3×a +66+60=12×a
12×a -6× a =288
6× a =288÷6
a = 48 km